2023-02-21 08:05:44

by Yu Kuai

Subject: [PATCH] block, bfq: free 'sync_bfqq' after bic_set_bfqq() in bfq_sync_bfqq_move()

From: Yu Kuai <[email protected]>

As explained in commit b600de2d7d3a ("block, bfq: fix uaf for bfqq in
bic_set_bfqq()"), bfqq should not be freed before bic_set_bfqq().
However, this is broken while merging commit 9778369a2d6c ("block, bfq:
split sync bfq_queues on a per-actuator basis") from branch
for-6.3/block.

Fixes: 9778369a2d6c ("block, bfq: split sync bfq_queues on a per-actuator basis")
Signed-off-by: Yu Kuai <[email protected]>
---
block/bfq-cgroup.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
index ea3638e06e04..89ffb3aa992c 100644
--- a/block/bfq-cgroup.c
+++ b/block/bfq-cgroup.c
@@ -746,8 +746,8 @@ static void bfq_sync_bfqq_move(struct bfq_data *bfqd,
* old cgroup.
*/
bfq_put_cooperator(sync_bfqq);
- bfq_release_process_ref(bfqd, sync_bfqq);
bic_set_bfqq(bic, NULL, true, act_idx);
+ bfq_release_process_ref(bfqd, sync_bfqq);
}
}

--
2.31.1

2023-02-21 09:14:39

by Damien Le Moal

Subject: Re: [PATCH] block, bfq: free 'sync_bfqq' after bic_set_bfqq() in bfq_sync_bfqq_move()

On 2/21/23 17:29, Yu Kuai wrote:
> From: Yu Kuai <[email protected]>
>
> As explained in commit b600de2d7d3a ("block, bfq: fix uaf for bfqq in
> bic_set_bfqq()"), bfqq should not be freed before bic_set_bfqq().
> However, this is broken while merging commit 9778369a2d6c ("block, bfq:
> split sync bfq_queues on a per-actuator basis") from branch
> for-6.3/block.

The patch looks OK to me, but the commit message is not super clear. What is
broken exactly ?

>
> Fixes: 9778369a2d6c ("block, bfq: split sync bfq_queues on a per-actuator basis")
> Signed-off-by: Yu Kuai <[email protected]>
> ---
> block/bfq-cgroup.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
> index ea3638e06e04..89ffb3aa992c 100644
> --- a/block/bfq-cgroup.c
> +++ b/block/bfq-cgroup.c
> @@ -746,8 +746,8 @@ static void bfq_sync_bfqq_move(struct bfq_data *bfqd,
> * old cgroup.
> */
> bfq_put_cooperator(sync_bfqq);
> - bfq_release_process_ref(bfqd, sync_bfqq);
> bic_set_bfqq(bic, NULL, true, act_idx);
> + bfq_release_process_ref(bfqd, sync_bfqq);
> }
> }
>

--
Damien Le Moal
Western Digital Research

2023-02-21 09:35:52

by Yu Kuai

Subject: Re: [PATCH] block, bfq: free 'sync_bfqq' after bic_set_bfqq() in bfq_sync_bfqq_move()

Hi,

在 2023/02/21 17:14, Damien Le Moal 写道:
> On 2/21/23 17:29, Yu Kuai wrote:
>> From: Yu Kuai <[email protected]>
>>
>> As explained in commit b600de2d7d3a ("block, bfq: fix uaf for bfqq in
>> bic_set_bfqq()"), bfqq should not be freed before bic_set_bfqq().
>> However, this is broken while merging commit 9778369a2d6c ("block, bfq:
>> split sync bfq_queues on a per-actuator basis") from branch
>> for-6.3/block.
>
> The patch looks OK to me, but the commit message is not super clear. What is
> broken exactly ?

1) bfq_sync_bfqq_move() is introduced in commit 9778369a2d6c ("block,
bfq: split sync bfq_queues on a per-actuator basis"), which is merged to
block/for-6.3 branch.

2) commit 64dc8c732f5c ("block, bfq: fix possible uaf for 'bfqq->bic'")
is merged to mainline.

3) later, the fix for 2) b600de2d7d3a ("block, bfq: fix uaf for bfqq in
bic_set_bfqq()") is merged to mainline as well, however,
bfq_sync_bfqq_move() in block/for-6.3 branch is not changed.

4) At last, 1) is merged to mainline and bfq_sync_bfqq_move() is
still problematic.

Thanks,
Kuai
>
>>
>> Fixes: 9778369a2d6c ("block, bfq: split sync bfq_queues on a per-actuator basis")
>> Signed-off-by: Yu Kuai <[email protected]>
>> ---
>> block/bfq-cgroup.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
>> index ea3638e06e04..89ffb3aa992c 100644
>> --- a/block/bfq-cgroup.c
>> +++ b/block/bfq-cgroup.c
>> @@ -746,8 +746,8 @@ static void bfq_sync_bfqq_move(struct bfq_data *bfqd,
>> * old cgroup.
>> */
>> bfq_put_cooperator(sync_bfqq);
>> - bfq_release_process_ref(bfqd, sync_bfqq);
>> bic_set_bfqq(bic, NULL, true, act_idx);
>> + bfq_release_process_ref(bfqd, sync_bfqq);
>> }
>> }
>>
>

2023-02-22 00:04:32

by Jens Axboe

Subject: Re: [PATCH] block, bfq: free 'sync_bfqq' after bic_set_bfqq() in bfq_sync_bfqq_move()

On 2/21/23 1:29 AM, Yu Kuai wrote:
> From: Yu Kuai <[email protected]>
>
> As explained in commit b600de2d7d3a ("block, bfq: fix uaf for bfqq in
> bic_set_bfqq()"), bfqq should not be freed before bic_set_bfqq().
> However, this is broken while merging commit 9778369a2d6c ("block, bfq:
> split sync bfq_queues on a per-actuator basis") from branch
> for-6.3/block.
>
> Fixes: 9778369a2d6c ("block, bfq: split sync bfq_queues on a per-actuator basis")
> Signed-off-by: Yu Kuai <[email protected]>
> ---
> block/bfq-cgroup.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
> index ea3638e06e04..89ffb3aa992c 100644
> --- a/block/bfq-cgroup.c
> +++ b/block/bfq-cgroup.c
> @@ -746,8 +746,8 @@ static void bfq_sync_bfqq_move(struct bfq_data *bfqd,
> * old cgroup.
> */
> bfq_put_cooperator(sync_bfqq);
> - bfq_release_process_ref(bfqd, sync_bfqq);
> bic_set_bfqq(bic, NULL, true, act_idx);
> + bfq_release_process_ref(bfqd, sync_bfqq);
> }
> }

This is already in -git, see my reply to Linus. Eg this will apply
to for-6.3/block, but it will not apply to current master that
has it merged because we got that from the 6.2 side.

--
Jens Axboe